The present invention relates to the drive circuit chip mounting structure for use in a display device, and, more particularly, to a so-called flip-chip mounting type (or a chip-on-glass type) display device in which drive circuit chips are directly mounted on the periphery of a substrate which constitutes a display panel of the display device.
An active matrix type display device, which includes active elements, such as thin film transistors, for respective pixels and performs a switching driving of these active elements, is a known type of panel type display device, and it is exemplified by a liquid crystal display device or an organic EL display device. The present invention is characterized by the mounting structure of the drive circuit chips on a display panel which is applied to this type of panel type display device. Since the mounting structure of the drive circuit chips is substantially the same among the different panel type display devices, such as a liquid crystal display device and an organic EL display device, the mounting structure of the drive circuit chips will be explained hereinafter using a liquid crystal display device which employs a liquid crystal panel as an example.
For example, as an active matrix type liquid crystal display device which uses thin film transistors as active elements, a display device which adopts the mounting method which is referred to as a so-called flip-chip mounting method (FCA method) or a chip-on-glass mounting method (COG method) has been known, and such a display device has the following constitution. That is, a liquid crystal layer is sealed between a pair of insulation substrates, which are preferably made of glass plate, and a large number of pixels are arranged in a matrix array formed on a display region thereof. Further, input/output wiring lines for supplying display signals and voltages for displaying images to the pixels are formed on the outside of the display region on one insulation substrate. At least one drive circuit chip is directly mounted along a periphery of the insulation substrate and is connected with the terminal portions of the above-mentioned input/output wiring lines by way of an anisotropic conductive film having adhesiveness.
In such an active matrix type liquid crystal display device, a liquid crystal drive voltage (a gray scale voltage) is applied to pixel electrodes by way of the thin film transistors, and, hence, there is no crosstalk between the respective pixels. Accordingly, the active matrix type liquid crystal display device can produce a multi-gray-scale display without using a particular drive method for preventing crosstalk, which is different from the simple matrix type display device.
FIG. 11 is a plan view which schematically illustrates an example of the arrangement and structure of the periphery of the drive circuit chip mounted on the end periphery of one substrate of the liquid crystal display panel. Further, FIG. 12 is a plan view showing a state in which a flexible printed circuit board is mounted on the drive circuit power source inputting lines shown in FIG. 11. In FIG. 11 and FIG. 12, the drive circuit chip IC, which is mounted on the outside of the display region of one insulation substrate, has projecting terminals (hereinafter referred to as bumps) on a mounting surface (a surface which faces a main surface of the insulation substrate, also referred to as a circuit surface or a front-side surface) thereof. These bumps are connected with line terminals which are formed on the main surface of the insulation substrate. In FIG. 11 and FIG. 12, theses bumps are indicated by squares. The insulation substrate is provided with input/output wiring lines LL which supply drive signals and voltages from an external signal source to input/output bumps I/O-BUMP formed on a short side of the drive circuit chip IC with respect to one of a plurality of drive circuit chips IC and which sequentially transfer the drive signals and voltages to another one of the plurality of drive circuit chips IC arranged close to the drive circuit chip (drive circuit chips IC positioned next to the above-mentioned one drive circuit chip IC). Terminal portions which are electrically connected with the bumps are formed on one end of the respective wiring lines, for example.
Further, on one of the long sides (end periphery sides of the insulation substrate) of the drive circuit chip IC, data output bumps D-BUMP, which are connected with data wiring lines (drain-line lead lines) DTM that extend on the insulation substrate from the display region, and power source input bumps P-BUMP, which are connected with the drive circuit power source input wiring lines LLP, are formed. Here, among these bumps, dummy bumps are included for averaging the mounting gap between the drive circuit chip IC and the insulation substrate. In the drawing, a bold crucifix symbol represents an alignment mark for positioning at the time of mounting.
The drive circuit chip IC is mounted on the main surface of the insulation substrate by aligning the positions of the plurality of bumps formed on the mounting surface thereof and the positions of the plurality of wiring lines (input/output wiring lines) formed on the main surface of the insulation substrate corresponding to the plurality of bumps; and, thereafter, it is adhered to the insulation substrate by thermo-compression bonding the plurality of bumps and the plurality of wiring lines by way of an anisotropic conductive film. Such a mounting method is referred to above as the flip-chip method (FCA method) or the chip-on-glass method (COG method). Further, a flexible printed circuit board FPC2 also has the wiring lines thereof fixed to the drive circuit power source input wiring lines LLP by thermo compression bonding in the same manner using the anisotropic conductive film. Hereinafter, the term “chip on glass mounting method (COG method) will be used.
Here, with respect to a liquid crystal display device which mounts a drive circuit chip on an insulation substrate using the COG method, reference is made to Patent Document 1. The Patent Document 1 describes a technique in which dummy bumps are formed on four corners of a drive circuit chip so as to enable confirmation of the positioning and the compression-bonded state by the naked eye at the time of mounting.
[Patent Document 1]
JP-A-11-125837